Pneumatic brake systems having flexible air hoses are typically used between adjacent railroad cars and with certain types of trucks. A coupling member is attached to each end of a flexible air hose for detachably connecting the air hose sections together. The sections extend from the braking system of each car when the individual railroad cars are joined to form a unit train. These coupling members, which are joined together by a rotational downward motion, engage mating flanges and lips that extend from the housings of the coupling member. In most instances the coupling members are suspended between the cars and hang a short distance above the railroad tracks. Occasionally, the coupling members become uncoupled prematurely when the hoses are subjected to a sudden upward movement caused by the motion of the railroad cars. This accidental separation of the coupling members between two sections of air hose during the operation of the train causes the emergency brakes to be applied resulting in delay and inconvenience and presenting potential safety problems.
It is desirable, therefore, to have an anti-disconnect device that prevents inadvertent rotational disengagement. It is further desirable, however, that the anti-disconnect device not prevent disengagement when a longitudinal force is applied along the length of the hoses such as occurs when two cars are uncoupled.
U.S. Pat. Nos. 3,892,431, 3,879,066 and 5,388,864 disclose examples of known locking devices for air brake hoses. The device in the '431 patent requires that a spring loaded outwardly extending member be manually depressed before the coupling housings may be engaged or separated by rotating the coupling housings with respect to each other. The '066 patent discloses a locking device that is gravity activated. The '864 patent discloses a locking device that is manually operated by railroad employees when they are engaging the air hoses between the cars.
In the standard pneumatic braking system, the air pressure in the system maintains the brakes in an "off" position. Activation of the braking system is caused by a drop in the pressure. A locking system to prevent accidental disengagement is limited to one that is independent of the amount of pressure in the pneumatic brake lines or ones that must work within the normal operating range of the brake system, usually 50 to 90 p.s.i. The braking systems of the prior art are manually operated.
In an electro-pneumatic operated brake system, on the other hand, the air pressure in the hoses is held constant. The brakes are activated by electrical signals rather than by fluctuations in the pressure in the air hoses. Thus, it is desirable for the electro-pneumatic system to have a locking system that is automatically engaged when the system is pressurized.